News Corp, MySpace's current parent company, bought MySpace for an exorbitant $580 million five years ago,
back when MySpace was still king of the social networking world, but
it's rapidly lost ground to Facebook in the years since. The statement from MySpace, written by Jon Miller, Chief Digital Operator of News Corp:

We fully respect Jason’s decision to leave and his personal desire to return to New York. As many people know, Jason is like family to me, and as expected, he’s done everything we asked of him and more. We’re incredibly grateful for the passion and enthusiasm he brought to the company. And as I know Jason agrees, Mike Jones has done an outstanding job leading MySpace into its next evolution and is the right person to take the reins. There are no plans to bring in additional management.

Hirschhorn confirmed the departure on Twitter, saying:

Yes i am moving back to NYC. Concrete jungle where dreams are made of. I believe in MySpace, its leader Jonesy and its wonderful team.